Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 539 PM EST Fri Dec 29 2023 Valid 12Z Tue Jan 2 2024 - 12Z Sat Jan 6 2024 ***Windy conditions for the Arctic Coast, the Aleutians, and portions of the mainland*** ...General Overview... A powerful surface low is expected to develop over the North Pacific and then approach the Aleutians going into Tuesday, potentially 950mb or even lower at the low reaches maximum intensity and then crosses over Bristol Bay going into Wednesday. Meanwhile, an arctic surface high is expected to be in place several hundred miles north of the Arctic Coast, and this will create an impressive pressure gradient across the entire state and strong winds across much of the mainland and especially the Aleutians and Alaska Peninsula. This low gradually weakens by the end of the week across the western mainland, followed by a second low pressure system becoming better organized just south of the central Aleutians by Friday. ...Guidance Evaluation/Preferences... All of the deterministic guidance continues to depict a very strong low pressure system in the general vicinity of the central/eastern Aleutians and Bristol Bay for the Tuesday-Wednesday time period. Similar to yesterday, the 12Z GFS has the low position a few hundred miles east of the model consensus (CMC/ECMWF/ensemble means), so this solution was weighted less in the forecast blend for fronts and pressures. The CMC indicates a faster weakening of the low compared to the GFS/ECMWF, but still within the realm of possibility. However, the CMC differs more with the next low pressure system moving in by late in the forecast period with the low well to the east of the ECENS/GEFS means, so it was weighted less for days 7 and 8. The use of the ensemble means increased to about 50% by next Saturday. ...Weather/Hazards Highlights... The expected flow pattern leads to higher confidence in rounds of heavy precipitation (coastal rains, with heavy snow at higher elevations and inland) near south-central Alaska, particularly on January 2nd, as the large and deep cyclone slowly moves in from the west. Widespread gale to storm-force winds are expected to begin the New Year across the Arctic Coast and adjacent portions of the North Slope, Kotzebue Sound, Norton Sound, the Aleutians, and the usual favored locations in southern Alaska, all driven by a potential 90-100 mb pressure gradient between the Arctic Ocean and the Aleutians/southern Bering Sea! This storm will also be accompanied by wave/swell threats across the Bering and North Pacific, and ground blizzard conditions for the Arctic Coast region. Temperatures across western and southern Alaska should warm to above average levels while colder weather across the North Slope and eastern interior persists longer. Hamrick Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can also be found at: https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html